Pathophysiological of pnemoperitoneum in Laparoscopic surgery

Pathophysiological of pnemoperitoneum in Laparoscopic surgery

1.   Cardiovascular system
Cardiovascular effects of pneumoperitoneum occur most often during its induction, and this should be considered when initial pressure is raised for introduction of access devices. In ASA I-II patients, the haemodynamic and circulatory effects of a 12 - 14 mmHg capnoperitoneum are generally not clinically relevant (grade A). Due to the haemodynamic changes in ASA III-IV patients, however, invasive measurement of blood pressure or circulating volume should be considered (grade A). These patients also should receive adequate preoperative volume-loading (grade A), beta-blockers (grade A), and intermittent sequential pneumatic compression of the lower limbs, especially in prolonged laparoscopic procedures (grade C). If technically feasible, gasless or low-pressure laparoscopy might be an alternative for patients with limited cardiac function (grade B). The use of other gases (e.g. helium) showed no clinically relevant haemodynamic advantages (grade A).

2.   Lung physiology and gas exchange
Carbon dioxide pneumoperitoneum causes hypercapnia and respiratory acidosis. During laparoscopy, monitoring of end-tidal CO2 concentration is mandatory (grade A) and minute volume of ventilation should be increased in order to maintain normocapnia. Increased intraabdominal pressure and head-down position reduce pulmonary compliance and lead to ventilation-perfusion mismatch (grade A). In patients with normal lung function, these intra-operative respiratory changes are usually not clinically relevant (grade A). In patients with limited pulmonary reserves, capnoperitoneum carries an increased risk of CO2-retention, especially in the postoperative period (grade A). In patients with cardiopulmonary diseases, intra- and postoperative arterial blood gas monitoring is recommended (grade A). Lowering intraabdominal pressure and controlling hyperventilation reduce respiratory acidosis during pneumoperitoneum (grade A). Gasless laparoscopy, low-pressure capnoperitoneum, or the use of helium might be an alternative for patients with limited pulmonary function (grade B). Laparoscopic surgery preserves postoperative pulmonary function better than open surgery (grade A).

3.   Venous blood return
During laparoscopy, both head-up position and elevated intra-abdominal pressure independently reduce venous blood return from the lower extremities (grade A). Intraoperative sequential intermittent pneumatic compression of the lower extremities effectively reduces venous stasis during pneumoperitoneum (grade A/B) and is recommended for all prolonged laparoscopic procedures. The true incidence of thromboembolic complications after pneumoperitoneum is not known.

4.   Perfusion of intraabdominal organs
Although in healthy subjects (ASA I-II), changes in kidney or liver perfusion (grade A) and also splanchnic perfusion (grade D) due to an intraabdominal pressure of 12-14 mmHg have no clinically relevant effects on organ function, this may not be the case in patients with already impaired perfusion. Especially, in patients with impaired hepatic or renal function or atherosclerosis, the intraabdominal pressure should be as low as possible to reduce microcirculatory disturbances (grade B). Patients with impaired renal function should be adequately volume loaded before and during elevated intraabdominal pressure (grade A).

5.   Stress response and immunologic parameters
Changes in systemic inflammatory and anti-inflammatory parameters (mainly cytokines) as well as in stress response parameters are less pronounced after laparoscopic surgery than after conventional surgery (grade A). Whether this leads to clinically relevant effects (eg less pain, fatigue and complications), remains to be proven. There is no compelling clinical evidence that specific modifications of the pneumoperitoneum alters the immunological response.

6.   Peritonitis
Presupposing appropriate perioperative measures (e.g. adequate preoperative volume loading) and haemodynamic stability, there are no contraindications to create a pneumoperitoneum when laparoscopic surgery is applicable in cases of peritonitis (grade B). The results from animal studies about the influence of pneumoperitoneum upon bacteraemia and endotoxaemia are controversial.

7.   Risk of tumor spreading
Until now, there is no strong clinical evidence (except case reports) that pneumoperitoneum in patients with intraabdominal malignant disease increases the risk of tumor spread (grade D). The panel considers there is no reason to contraindicate pneumoperitoneum in these patients, given the fact that an approppriate operative technique is used (grade C). The type of insufflation gas seems to affect intraabdominal tumor growth, while intraabdominal pressure is of little importance (grade D). Due to the low level of evidence, patients undergoing laparoscopic surgery for malignant disease should be included in randomised controlled trials or at least in quality registries.

   Establishing the pneumoperitoneum

1.   Creation of a pneumoperitoneum
For severe complications (vessel perforation) it is impossible to prove a difference between closed and open access technique in RCTs, therefore, large outcome studies should be considered. In the RCTs, the rate of major and minor complications is surprisingly high, which may be due to the definition of a complication or surgical learning curve. Insertion of the first trocar with the open technique is faster as compared to the Veress needle (grade A). The randomised controlled trials comparing closed (Veress plus trocar) versus open approach have inadequate sample size to find a difference in serious complications. In large outcomes studies there were less complications in the closed group (grade B). Although RCTs found the open approach faster and associated with a lower incidence of minor complications (grade A), the panel cannot favour the use of either access technique. However, the use of either techniques may have advantages in specific patient subgroups (grade B).

2.   Gas embolism and its prevention
Clinically relevant gas embolism is a very rare, but if it occurs, may be a fatal complication (grade C). The true incidence of clinically inapparent gas embolism is not known. Most cases of gas embolism described have been caused by accidental vessel punction with a Veress needle at the induction of pneumoperitoneum. Low intraabdominal pressure, low insufflation rates, as well as careful surgical technique may reduce the incidence of gas embolism (grade D). A sudden drop in end tidal CO2 concentration and blood pressure during abdominal insufflation should be considered a sign of gas embolism (grade C). Due to the low incidence of clinically relevant gas embolisms, an advanced invasive monitoring (transoesophageal Doppler sonography) cannot be recommended for clinical routine (grade B).

3.   Choice of insufflation pressure
The panel recommends to use the lowest intraabdominal pressure allowing adequate exposure of the operative field, rather than using a routine pressure (grade B). An intraabdominal pressure lower than 14 mmHg is considered safe in a healthy patient (grade A). Abdominal wall lifting devices have no clinically relevant advantages compared to low-pressure (5-7 mmHg) pneumoperitoneum (grade B).

4.   Warming and humidifying of insufflation gas
Warming and humidifying insufflation gas is intended to decrease heat loss. Compared to external heating devices, however, the clinical effects of warmed, humidified insufflation gas are minor (grade B). Data on its influence on postoperative pain are contradictory (grade A).

5.   Abdominal wall lifting devices
Abdominal wall lifting as compared to capnoperitoneum results in less impairment of haemodynamic, pulmonary and renal function (grade A). In ASA I-II patients, the magnitude of these benefits is too small to recommend (grade D). In patients with limited cardiac, pulmonary or renal function, abdominal wall lifting combined with low-pressure pneumoperitoneum might be an alternative (grade C). Nevertheless, surgical handling and operative view were impaired in most surgical procedures (grade A).

6.   Size of access devices
Smaller access devices (< 5mm) in laparoscopy is only feasible in a selected group of patients. The use of 2-5mm instead of 5-10mm access devices improves cosmetic result and postoperative pain marginally in laparoscopic cholecystectomy (grade A).

III.   Postoperative aspects

1.   Adhesions
Some laparoscopic procedures may cause less postoperative adhesions as compared to their conventional counterparts (grade B). However, the specifics of a pneumoperitoneum (gas, pressure, temperature and humidity) seem to have no major effect on the development of postsurgical adhesions (grade D).

2.   Pain, nausea and vomiting
Pain after laparoscopic surgery is multifactorial and should be treated with a multi¬modal approach (grade A). Shape and size of access devices has to be considered (grade A). Low-pressure pneumoperitoneum, heated and humidified insufflation gas, incisional and intraperitoneal instillation of local anaesthetics, intraperitoneal instillation of saline, and removal of residual gas,  all reduce postlaparoscopic pain (grade B). Inconclusive data and small “effect sizes“ of singular approaches make it difficult to recommend these treatments in general (grade D). No evidence exists that the specifics of a pneumoperitoneum have any effect on postoperative nausea and vomiting.

3.   Pregnancy
Presupposing obstetrical consultation, laparoscopic procedures during pregnancy should be performed in the second trimester if possible (grade C). Perioperatively, maternal end-tidal CO2-concentration and arterial blood gases must be monitored to control maternal hyperventilation and to prevent fetal acidosis (grade C). For the establishment of the pneumoperitoneum the open technique should be preferred (grade C). During laparoscopy intraabdominal pressure should be kept as low as possible and body positioning should be considered in order to avoid inferior vena cava compression by the uterus (grade C). Furthermore, pneumatic compression devices are recommended (grade D).

4.   Intracranial pressure
Raised IAP and head-down position increase intracranial pressure (ICP) (grade A). Therefore, elevated IAP, head down position and hypoventilation should be avoided (grade D). In patients with head injury or neurological disorders, perioperative monitoring of ICP should be considered (grade C). Gasless laparoscopy might be an alternative to prevent ICP peaks (grade D).

5.   Abdominal trauma
Until now, there are no prospective studies evaluating the specifics of a pneumoperitoneum (type of gas, IAP, temperature) in patients with blunt or penetrating abdominal trauma (grade D).